Finding the Strongest Evidence Yet of Liquid Water on Mars Began Five Years Ago

Lujendra Ojha was a University of Arizona undergraduate student in 2010 when he noticed dark, narrow features called recurring slope lineae (RSL) on the surface of Mars. Today, Ojha is the lead author of a report providing strong evidence of liquid water flowing on present-day Mars.

What was the “significant development?” Hydrated salts. Using an imaging spectrometer on the Mars Reconnaissance Orbiter (MRO), the study’s authors detected signatures of hydrated minerals on slopes where the dark streaks are seen. These streaks appear on several spots on Mars when temperatures are above minus 10 degrees Fahrenheit. Then, they disappear when it’s colder.

The spectrometer only showed signatures of hydrated salts at relatively wide RSL. Observations made at the same locations when RSL were less extensive showed no hydrated salt.

Here’s Ojha explaining what they found.

“We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks,” said Ojha.

The image below shows the flows from Garni crater.

The dark streaks in the above image are up to a few hundred meters in length.

What the hydrated salts are made up of

From the release:

Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate.

Scientists have known about perchlorates on Mars for a while. NASA’s Phoenix lander and Curiosity rover detected them in the planet’s soil. They may have even been detected during the Viking missions in the 1970s.

This new data is a big deal because it’s the first time perchlorates have been identified from orbit. And the MRO and its six instruments made it possible.

“The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are,” said Rich Zurek, MRO project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

Today’s findings prove that Mars still has many secrets waiting to be revealed.

“It took multiple spacecraft over several years to solve this mystery, and now we know there is liquid water on the surface of this cold, desert planet,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program at the agency’s headquarters in Washington. “It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future.”